- Use of an investigational anti-cancer drug within 28 days or five half-lives with a minimum duration of 10 days from prior therapy preceding the first dose of GSK2256098/trametinib OR Chemotherapy within the last 3 weeks (6 weeks for prior nitrosourea or mitomycin C) OR any major surgery, radiotherapy, or immunotherapy within the last 4 weeks. NOTE: Limited palliative radiation (i.e., duration typically < 15 days) with last dose >=6 weeks preceding the first dose of combination treatment is acceptable provided subject meets all of the other eligibility criteria and radiotherapy port does not encompass all measurable tumor. In addition, prophylactic radiation therapy to the site of tumor biopsies (as per the standard of care) during the current study to prevent seeding of the needle tract/biopsy is acceptable and does not require dose modification.